SD vs XQD

[gilbouk]

Ah, OK, it is an SDXC card that is also UHS-II. So you are getting close to the maximum with your set up.

Sandisk have called various cards "Extreme Pro" over the years, to I think designate that as their fastest at that time. They still have 95MB/s cards on their site that is also called "Extreme Pro", and that is also SDXC, but UHS-I.

Aha, hence my confusion.

 

[gcgraphs]

And just to confuse us Amazon have an Extreme Pro 300MB/s SDHC with the UHS-3 symbol!

GC

 

[redhed17]

And I think if Kodiak put a slower card, such as a 95MB/s Sandisk Extreme Pro, it would not be able to go faster than 95MB/s. And if there is such a thing as Thunderbolt card reader that is not able to read the extra pins on the UHS-II cards, then the 300MB/s maximum could not be reached.

I think in theory the maximum UHS-I speed is 104MB/s if all hardware and software is working at max.

 

[redhed17]

And just to confuse us Amazon have an Extreme Pro 300MB/s SDHC with the UHS-3 symbol!

GC

And to confuse even more, from Wiki;

UHS-I and UHS-II cards can use UHS Speed Class rating with two possible grades: class 1 for minimum read/write performance of at least 10 MB/s ('U1' symbol featuring number 1 inside 'U') and class 3 for minimum write performance of 30 MB/s ('U3' symbol featuring 3 inside 'U'), targeted at recording 4K video. Before November 2013, the rating was branded UHS Speed Grade and contained grades 0 (no symbol) and 1 ('U1' symbol). Manufacturers can also display standard speed class symbols (C2, C4, C6, and C10) alongside, or in place of UHS speed class.

So it seems the U with a number in is separate from being UHS-I or UHS-II. It needs to be a UHS-II card to get the faster speeds above 104/s as they have the extra row of connection pins to transfer more data. The socket that the card goes into also needs to be compatible too. I don't think the socket on my laptop is, but Kodiak's card reader is.